1. Field of the Invention
The present invention relates to an ink jet recording medium that can be suitably used for an ink jet recording method using an ink containing pigment.
2. Description of the Related Art
Heretofore, as an ink jet recording medium used for an image formation by an ink jet recording method, there have been known mediums having a variety of constitutions. Nowadays, however, it has come to be used for the output of electronic image information for computers and networks as well as for the output or the like of image information collected by digital cameras, digital videos, scanners, and the like. In this way, widened applications and improved functions of the recording apparatus (printer) by the ink jet recording method are recently noticeable. Hence, demands for the performance of the ink jet recording medium has become further diversified and become those for higher levels.
With development of the higher resolution of the output image as described above, the amount of ink printed on a recording medium from an ink jet printer has a tendency to increase. Hence, as the ink jet recording medium of a high absorption type capable of receiving a large amount of ink, a recording medium provided with an ink receiving layer including inorganic porous particles, such as silica and alumina hydrate, and a binder, such as water soluble resin, on a substrate has come to be used. This recording medium can enhance ink absorbency by allowing the inorganic porous particles to absorb dyes in the ink.
On the other hand, while water soluble dyes have been widely used in the prior art as an ink for the ink jet, an aqueous ink including a pigment as a coloring material has come to be used with a view to improving weather resistance of the ink jet recording medium. The ink jet recording medium using the aqueous pigment ink as described is, as compared with recorded products using a dye ink, extremely excellent with regards to discoloration due to the light such as ultraviolet rays and discoloration of the image caused by a slight amount of gas existing in the atmospheric environment.
Here, the size of pigment particles (hereinafter, referred to as “pigment ink particles”) in the pigment ink is generally about 100 nm. Hence, when the conventional ink jet recording medium including the alumina hydrate of not less than 100 nm and not more than 200 nm in particle size and the inorganic particles such as silica is used, printed pigment ink particles remain on the uppermost layer portion of the ink receiving layer of the ink jet recording medium. Consequently, color developability of the printed product is extremely excellent, and its glossiness becomes also excellent. On the other hand, however, the pigment ink particles merely stick to the ink jet recording medium surface, and this has caused a problem that the pigment ink is liable to be scraped off by scratching and the like with a result that the image becomes extremely vulnerable (weak in scratch-resistance performance).
Further, as another ink jet recording medium, an ink jet recording medium having an ink receiving layer including wet silica and the like of about several μm in particle size can be cited. When this ink jet recording medium is used, printed pigment ink particles penetrate into a gap between the inorganic particles of about several μm comprising the recording medium and reach the inner most place of the ink receiving layer, so the pigment ink particles do not remain on the uppermost surface of the ink receiving layer. Hence, while being excellent in scratch-resistance, since the pigment ink particles have sank deep into the ink receiving layer, sufficient color development performance of the printed product has not been obtained.
Further, nowadays, as a substitute for silver halide photography, a so-called glossy paper having a 20° specular gloss of not less than 10% according to JIS-Z-8741 is required as the ink jet recording medium. Here, to be excellent in scratch resistance, when a wet silica of about several μm was used, only a non-glossy matte paper having a 20° specular gloss of not more than 1% has been able to be obtained as an ink jet recording medium. This has created a problem that the characteristic required as a glossy paper is not satisfied.
Hence, heretofore, the manufacture of an ink jet recording medium that can achieve excellent image properties has been attempted, which allows coloring materials to remain on the surface, and at the same time, has excellent scratch resistance after fixing the coloring materials on the surface.
Japanese Patent Application Laid-Open No. 2001-287442 describes a method of improving high gloss and image quality by allowing the surface of an ink receiving layer to have a crack and controlling the size of the crack. However, in the ink receiving layer having such a crack, similarly to the case where wet silica of about several μm in particle size is used, pigment ink particles reach the deepest place of the ink receiving layer from the crack, and the particle was hard to be fixed on the surface layer portion. For this reason, in the ink jet recording medium having printed pigment ink, color developability has been insufficient.
Further, with respect to the ink jet recording medium using the pigment ink, Japanese Patent Application Laid-Open No. 2002-307810 and Japanese Patent Application Laid-Open No. 2004-268287 describe a recording medium defining the surface roughness. However, in these ink jet recording mediums, achievement of both high color developability and high glossiness of a printed product, and improvement (improvement of scratch resistance performance) again vulnerability of a printed product has not been sufficiently studied.